Energy From Evaporation Could Power Much of US, Study Finds

Evaporation-harvested energy can cut by half the water lost to natural evaporation, researchers say. Water-strapped cities with growing populations and energy needs could benefit most, including greater Phoenix, served by the above reservoir and irrigation system fed by the Colorado River. (Photo: Central Arizona Project)

(CN) – As the landscape of potential sources of renewable energy continues to expand and change, power derived from evaporation could serve as a robust and bio-friendly option for the United States and other nations, scientists reported Tuesday.

While solar and wind power are limited by day-to-day fluctuations, energy harvested from evaporation could be a solution for regions in which climate conditions vary greatly, as well as for nations where existing renewable sources are insufficient.

In the first evaluation of evaporation as a possible source of energy, a new study finds that it could ultimately generate about 325 gigawatts of power, nearly 70 percent of what the United States currently produces.

“We have the technology to harness energy from wind, water and the sun, but evaporation is just as powerful,” said senior author Ozgur Sahin, a biophysicist at Columbia University. “We can now put a number on its potential.”

Evaporation is how nature cycles water between land and air, and Sahin has previously shown how this natural process can be harnessed for energy. A machine developed in his lab, the Evaporation Engine, can control humidity with a shutter that opens and closes, triggering bacterial spores to expand and contract. The spores’ contractions are then transferred to a generator that produces electricity.

Tuesday’s study was designed to determine how much power this process could theoretically generate.

The team tested the evaporation technology by modeling its potential to generate energy from open bodies of freshwater like lakes and reservoirs across the United States, where weather-station data are readily accessible. The researchers excluded prime locations like rivers, coastlines and the Great Lakes to limit errors associated with modeling more nuanced interactions.

Among the advantages of using evaporation as an energy source is that it power can be generated when needed. With solar and wind power, on the other hand, batteries are needed to supply energy when the sun isn’t shining and wind is negligible.

“Evaporation comes with a natural battery,” said lead author Ahmet-Hamdi Cavusoglu, a graduate student at Columbia. “You can make it your main source of power and draw on solar and wind when they’re available.”

In addition to providing energy, evaporation technology can also save water. The team estimates that roughly half of the water that evaporates naturally from reservoirs and lakes into the atmosphere could be saved using the technology. According to their model, the energy-harvesting process could save about 25 trillion gallons of water a year, or about one-fifth of the water Americans consume.

Klaus Lackner, a physicist at Arizona State University, applauded the team’s findings. Lackner, who was not involved in the study, is developing artificial trees that pull carbon dioxide from the air which rely, in part, on harnessing the power of evaporation.

The southern and western United States have the greatest capacity to produce evaporation-generated power from lakes and reservoirs, a new study in Nature Communications finds. (Columbia University)

“Evaporation has the potential to do a lot of work,” he said. “It’s nice to see that drying and wetting cycles can also be used to collect mechanical energy.”

States and nations with sunny weather and growing populations are best suited to capitalize on evaporation technology’s capacity to generate energy and reduce water waste, as evaporation packs more energy in warm and arid conditions, according to the team. Drought-prone California, Nevada and Arizona are among the states that could benefit the most.

The team is trying to improve the energy efficiency of their spore-studded materials, and hope to eventually test their technology on a reservoir, lake or greenhouse, where it could simultaneously generate power and limit water loss.